Cigarette smoking is the world's single most preventable cause of disease and death. Worldwide, about 36 percent of all adults smoke cigarettes. According to a 1999 World Health Organization estimate, there are 4 million deaths a year from tobacco. Tobacco smoke contains more than 4000 compounds. Among these, nicotine is the habit forming pharmacological agent. Others are toxins, mutagens and carcinogens that cause or enhance various degenerative diseases including cancer of lung and other organs, chronic obstructive pulmonary disease such as bronchitis and emphysema as well as heart disease and stroke. Since approaches to cessation of smoking by public health campaigns and anti-smoking laws passed by local Governments have had limited success, the most practicable approach is the prevention of the hazardous effects caused by cigarette smoke. Modification of the cigarette is in itself a practical approach to reducing the toxic compounds contained in cigarette smoke. One of the approaches was to use cigarette filters. This is what the cigarette manufacturers have been trying to do for the last few decades.
The cigarette companies have introduced cigarettes with filter tips to reduce the harmful compounds in the smoke, apparently to produce safer cigarettes without affecting the flavour and nicotine content of the smoke. There are four main types of filters in use to-day, namely, cellulose acetate, polypropylene, pure cellulose and filters containing granular additives, mainly activated charcoal (1). Cellulose acetate dominates the global filter market with 68 percent. Polypropylene filters follow with 21 percent (almost all of which are in China), charcoal filters comprise 10 percent and cellulose filters comprise less than 1 percent. Since it is difficult in selectively reducing specific compounds, the companies have focused on reducing the tar components, which is thought to contain the majority of harmful compounds. This was the reason of the wide utilization of cellulose acetate filter tips. While this process is effective for reducing a little portion of the tar, it is not at all selective for individual compounds, particularly the gaseous and vapour phase components of cigarette smoke. However, tar is a poor concept as a basis for regulating tobacco. It is known that different brands of cigarettes produce tars with greatly varying concentrations of key toxins. Many people smoke low tar/low nicotine products believing that smoking these products are safer or will reduce their risks of cancer and other diseases. However, in doing so they typically change the way they smoke to get more nicotine. In order to compensate for lower levels of nicotine, many smokers often take bigger, deeper or more frequent puffs or smoke more cigarettes to obtain their needed levels of nicotine. Therefore, their exposure to toxins is not really reduced.
This is why health scientists do not consider ‘lights’ or ‘ultra lights’ cigarettes as reliably less hazardous. In fact, till date there is no such thing as a safe cigarette. Obviously, such cigarettes with lower tar and nicotine content many be a distracting illusion of reduced harm and may not give any health benefit. This is particularly because the factors of cigarette smoke, which contribute to the known risks, are still not clearly defined. We consider that reducing the undesirable compounds in smoke is certainly of great importance, but selectively reducing the most undesirable compound is likely to be the most effective way of lowering the risk of smoking.
Activated charcoal filters seem to be better than cellulose acetate filters. These filters remove significant amounts of some toxic and irritant gases and semivolatile organic compounds, which the cellulose filters, do not. However, there is presently no data directly linking the use of commercially available charcoal filters to lowered risk of smoking. It would have been ideal to pinpoint one compound or a group of compounds as the main culprit in cigarette smoke and to use a filter to selectively reduce this. Since the factors in cigarette smoke that contribute to the known risks are not clearly understood, a clear definition of a safer or lower risk cigarettes does not exist. In fact, there is no existing parameter by which toxicity or carcinogenic potential of a particular brand of cigarette can be measured.
Nevertheless, at present the most discussed carcinogens and toxins are the tobacco specific nitrosamines (TSNA) particularly, N-nitrosonornicotine (NNN) and 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK), polynuclear aromatic hydrocarbons (PAH) such as benzo(a) pyrene, aldehydes (e.g. acetaldehyde, crotonaldehyde), volatile hydrocarbons (benzene, toluene), aromatic amines, trace materials as well as carbon monoxide, nitric oxide, acrolein and phenol. However, it is yet to be known which of these carcinogens toxins is most harmful and whether removal of all these will reduce the risks of smoking and incidence of cancer. For many years it has been believed that polycyclic aromatic hydrocarbons, particularly benzo(a) pyrene, play a major role in the development of lung cancer.
Nowadays, TSNAS are the focus of a lot of attention. However, just because these compounds can cause cancer or other diseases on their own, they are not necessarily responsible for cancers or other diseases resulting from tobacco smoke. The carcinogens present in tobacco smoke are at such small concentrations that it is highly unlikely that one would cause cancer or other diseases on its own. For example, the concentration of benzo(a) pyrene in the mainstream cigarette smoke is in the range of 10 to 40 ng (2) and the average amount of both NNK and NNN is 200 ng per cigarette (3). Moreover, not to-date there has been any single compound identified as more responsible than others for the risks associated with smoking. As indicated before, it would have been ideal to pinpoint the most hazardous compound in cigarette smoke and to eliminate it by the use of filters.
The applicants have reported before (4) that the aqueous extract of cigarette smoke contains some stable oxidant, which causes extensive oxidative damage of proteins. Very recently, the applicants have isolated the oxidant from cigarette smoke/tar solution and identified it as a major potentially hazardous compound, which almost quantitatively accounts for the oxidative damage of proteins caused by cigarette smoke solution. The chemical structure of the oxidant has been established to be p-benzosemiquinone (p-BSQ) as evidenced by elemental analysis, mass spectrum, UV, IR, NMR and ESR spectra as well as by chemical properties (5). p-BSQ is a relatively stable free radical, apparently because the unpaired electron is delocalised over an aromatic framework containing heteroatoms leading to different mesomeric forms, namely, anionic, neutral and cationic forms. The half-life of p-BSQ, as determined by its oxidant activity, is 48 hours in solid state at the room temperature and about 1.5 hours in aqueous solution at pH 7.4. We have examined 12 different brands of cigarettes including Indian, American, British, Russian and Japanese cigarettes. The content of p-BSQ in the mainstream smoke of these different brands varies from 104 μg to 200 μg depending on the brand of cigarette. Thus its concentration in the smoke is approximately 5000 to 11,000 times that of benzo(a) pyrene and 520 to 1000 times that of both NNK and NNN. Unlike PAH and TSNA, p-BSQ is a highly reactive strong oxidant which reacts directly with proteins. Besides being responsible for protein oxidation, pBSQ is also responsible for the oxidative damage of DNA. Since DNA oxidation is implicated with mutation and cancer, p-BSQ may be a major factor for the cause of cancer by cigarette smoke. Nagata et. al. have shown that semiquinone damages DNA(6). Pryor has shown that semiquinone free radicals are critically involved in causing DNA damage of a type that is not easily repaired and therefore may lead to mutation and cancer (7). The applicants have considered that toxicity of a particular brand of cigarette can be determined by measuring the level of p-BSQ in the mainstream smoke. Lower the level of p-BSQ; lesser is the toxicity.
Earlier observations of Pryor and his associates (8) suggested that the principal relatively stable radical in cigarette tar might be quinone/hydroquinone/semiquinone complex which was an active redox system and that this redox system was capable of reducing molecular oxygen to produce superoxide, leading to hydrogen peroxide and hydroxyl radicals, which may eventually lead to oxidative damage of biological macromolecules. Since cigarette tar was an incredibly complex mixture and since the tar radicals were not isolated and unambiguously identified, the conclusion of Pryor and his associates (8) concerning the chemistry or biochemistry of the tar radicals was regarded as tentative. The authors thought that the principal radical in tar was actually not a monoradical and probably not a single species. However, as mentioned before, we have observed that the major stable hazardous oxidant in cigarette smoke is a single species namely, p-BSQ. The oxidative damage of proteins produced by p-BSQ is not inhibited by SOD or catalase, affirming that the oxidative damage is not mediated by secondarily produced superoxide and hydrogen peroxide. We have further observed that p-BSQ oxidized protein in the nitrogen atmosphere in the absence of molecular oxygen (4), indicating that there is a direct interaction of p-BSQ and biological macromolecules.
The aforesaid results would indicate that p-BSQ is a major highly reactive harmful oxidant occurring in high concentrations in cigarette smoke, and it is possibly responsible for the oxidative damage of proteins and DNA leading to degenerative diseases and cancer. It would thus appear that on the one hand p-BSQ content in the smoke might be a parameter of toxicity of a particular brand of cigarette and on the other hand elimination of p-BSQ from the mainstream smoke will produce potentially less hazardous safer cigarettes. We have observed that cellulose acetate filter is ineffective in absorbing p-BSQ, but activated charcoal filters adsorbs it. Too much of charcoal in the filter not only eliminates p-BSQ but also drastically reduces the mouthful of smoke, nicotine content as well as the flavor and taste of the smoke. On the contrast, too little charcoal is ineffective in significant reduction of p-BSQ. In fact, elimination of p-BSQ from the smoke depends on the amount of particular grain size or grain sizes or combination of grain sizes of activated charcoal used. So, we have devised cigarette filters using stipulated amounts of specific grain sizes and also combination of grain sizes of activated charcoal to find out optimum filtering devices for effective reduction of p-BSQ from the mainstream smoke. Since activated charcoal is known to adsorb significant amounts of many of the toxic gas and vapor phase components of cigarette smoke, the said activated charcoal filters are expected not only to remove p-BSQ, which is conceived to pose the greatest health risk, but also many other toxic components thereby producing potentially less hazardous cigarettes.
Use of activated charcoal filter is not new. The most prominent forms of charcoal filters are cavity and dual filters made with carbon granules. Cavity filters are manufactured by placing carbon granules in a void space between two segments of cellulose acetate filter tow. Dual filters are produced by sprinkling carbon granules in cellulose acetate filter tow or cellulose or paper mesh. There are quite a number of reports and patents describing charcoal filtered cigarettes. In most cases, the cavity charcoal filters are comprised of activated charcoal mixed with other granular materials including proteins, silica gel, zeolite, alumina, and milled wheat or starch granules. In the dual charcoal filters, small amounts of activated charcoal granules are scatteredly embedded in cellulose acetate filter tow. Since charcoal filters can remove significant amounts of some toxic and irritant gases and vapors including hydrogen cyanide, acrolein and benzene from the gas/vapor phase of the smoke, many researchers believe that reducing exposure to toxic gases is likely to have some benefit to the consumer.
It should be mentioned that none of said cavity filters or dual charcoal filters provides data regarding the amount of specific grain sizes or combination of grain sizes of activated charcoal used in relation to the length of the cigarette selected and the level of p-BSQ in the mainstream smoke. The concept that the level of p-BSQ in the mainstream cigarette smoke may produce the greatest health risk was not known before. As stated earlier, in our recent investigation (5) we have indicated that p-BSQ is a major highly reactive harmful oxidant occurring in high concentrations in the smoke. We have observed that only those charcoal filters that contain stipulated amounts of specific grain sizes or combination of grain sizes of activated charcoal in relation to the length of the cigarette selected are effective in markedly reducing the level of p-BSQ from the mainstream smoke. Activated charcoal mixed with other granular materials or activated charcoal sprinkled in cellulose acetate filter tow is inefficient in significantly reducing the level of p-BSQ from the mainstream smoke.
In anticipation of a health crisis to be precipitated by the Smoking and Health Report of the US Surgeon General's Committee, Philip Morris in early sixties developed a charcoal filter named Saratoga. However, at that time, the relationship between the amount of specific grain sizes of activated charcoal and the level of p-BSQ in the smoke was not known. Moreover, the product as test marketed did not have good taste and was consequently abandoned (9).
U.S. Pat. No. 4,038,992 (10) refers to a granular composition for use in tobacco filters wherein the granules are a blend of 40 to 80% protein granules, prepared either from milk whey protein or egg white protein and 20 to 60% active charcoal granules having a grain size of 10 to 50 mesh, occasionally mixed with excipients including cellulose, starch, sugars, alumina, zeolite and silica gel. The objective was to remove nonspecifically deleterious compounds from tobacco smoke with particular reference to benzopyrene, phenol and tar. No mention was made about the proportion of the different mesh sizes of active charcoal used. In our experience, activated charcoal having grain sizes below BS 44 and particularly mixed with said proteins granules or other granular materials is not efficient in reducing p-BSQ from the mainstream smoke.
U.S. Pat. No. 5,909,736 (11) describes a filter for filtering tobacco smoke comprising activated charcoal impregnated with a biological substance selected from the group consisting of hemoglobin, lysates of erythrocytes and combinations thereof. No mention was made about the grain sizes and the amount of the activated charcoal used in relation to the length of the cigarette. Moreover we have observed that activated charcoal impregnated with hemoglobin solution or lysates of erythrocytes is ineffective for removing p-BSQ from the mainstream smoke.
U.S. Pat. No. 4,373,539 (12) describes a smoking device comprising a means to hold a coiled helical tube filled with compressed carbon or activated charcoal having an inside diameter of approximately one-eight inch (≈3.125 mm) and a length of approximately one and one-quarter inches (≈31.25 mm) which when uncoiled is approximately six inches (≈150 mm) long. The objective of the invention was to eliminate the harmful tar. No data was given about either the grain sizes of the activated charcoal used or the nicotine delivery in the mainstream smoke. In addition, no biological experimental data was provided to indicate that the smoke coming out of the said filter was less toxic. It is obvious that smoke passing through activated charcoal of such longer filtration route would have minimum nicotine level in the smoke. Since value of a filter depends on the extent that it can selectively remove tar constituents without removing nicotine, the said coiled helical tube-filtering device containing activated charcoal has little practical application.
WO Patent No. 9600019 (13) refers to a filter containing activated charcoal enriched with a biological substance containing Fe, Cu and/or complexes with a porphyrin ring and Fe bound in protein molecules. No data was provided about either the grain sizes of charcoal or the amount of charcoal used in relation to the length of the cigarette. As stated before, we have observed that activated charcoal enriched with the said biological substances is inefficient in reducing p-BSQ from the mainstream cigarette smoke.
U.S. Pat. No. 5,360,023 (14) describes a cigarette filter in which the filter element preferably includes two or more filter segments of which one of the segments includes a carbonaceous material e.g. an activated carbon materials or an activated charcoal material in a powdered or fine grain from. The carbonaceous material is preferably incorporated into the filter segment as a component of a paper, typically as a gathered paper web. The filter segment including the carbonaceous material is constructed so as to have a number of longitudinally extending channels or air passageways extending through that filter segment. The channels or air passageways are of a cross-sectional area such that particular phase components of mainstream smoke passing through the filter segment are not filtered by or do not interact to a significant degree with the carbonaceous material. In this case also the said filter segment containing the carbonaceous material neither describe the grain sizes of charcoal or the amount of charcoal used in relation to the length of the cigarette. Moreover, since the air channels were used for preventing significant interaction of the mainstream smoke with the carbonaceous material, the possibility of effective reduction of the level of p-BSQ from the smoke is not expected.
U.S. Pat. No. 3,658,069 (15) refers to a filter element containing about 50 mg of activated carbon. However, neither the grain sizes nor the amount of charcoal used in relation to the level of p-BSQ in the smoke has been described.
Recently a patent-pending Advance cigarette, made by Virginia-Star scientific Inc., contain specially cured tobacco with reduced level of nitrosamines and activated-charcoal filter is being marketed (16). The activated charcoal has been used for removing some toxic gases in cigarette smoke. However, data on the amount of specific grain sizes of activated charcoal in relation to the length of the cigarette and the level of p-BSQ in the mainstream smoke has not been given. Moreover, no scientific or biological experimental data has been provided.
A filtered tube named “Gizes's Silvertip Charbon activated charcoal filter tube” has been produced by RYO (17). These silvertip tubes are costly and manufactured for repeated use. However, we have observed that the charcoal filters, when used more than once become ineffective in reducing p-BSQ level from the mainstream smoke. Moreover, data on the amount of specific grain sizes of charcoal used in relation to the length of the cigarette selected is not given.
A cavity filter, named CAVIFLEX, has been developed by Baumgartner, where low amounts of activated carbon, occasionally mixed with certain inert material, e.g. milled wheat, are used to fill up the cavity (18). However the amount of specific grain sizes of charcoal used in relation to the length of the cigarette and the level of p-BSQ in the mainstream smoke are not known.
Among the commercial charcoal filter cigarettes available in the market, about less than 1 percent of American cigarettes and 2 percent of Russian cigarettes use charcoal filters. However, charcoal is most popular in Japan. Out of the total Japanese cigarette market, about 95 percent have charcoal filters. Charcoal is also popular in South Korea, where the most widely used charcoal filters (about 90 percent) contain activated carbon blended with zeolite. In Hungary and Venezuela cigarette market, 90–95 percent have charcoal filters. In most cases, the charcoal filter contains small amount of activated charcoal granules distributed in some porous material or embedded within cellulose acetate filter tow. Charcoal filters in general reduce gaseous toxins in the smoke. But no evidence exists that the already available commercial charcoal filter cigarettes are significantly less dangerous for the users. We have examined one brand of Russian charcoal filter cigarette and one brand of mild Japanese charcoal filter cigarette containing low tar and low nicotine. The Russian cigarette had about 16-mg tar, 590-μg nicotine and 128 μg of p-BSQ in the mainstream smoke. The Japanese cigarette had about 12-mg tar, 500-μg nicotine and 104-μg p-BSQ in the smoke. The Russian cigarette contained about 10 mg of charcoal and the Japanese cigarette about 30 mg of charcoal scatterly embedded in cellulose acetate filter tow. The applicants observed that the p-BSQ content of the smoke from both the cigarettes remained unaltered irrespective of whether the charcoal filter was present or replaced by similar length of conventional cellulose acetate filter. This would indicate that the charcoal filters incorporated in both the Russian and the Japanese cigarettes were ineffective in reducing p-BSQ content of the mainstream smoke. As would be expected, BSA oxidation by the aqueous extract of CS from both the Russian cigarette (7.5±0.2 nmoles of carbonyl/mg BSA) and mild Japanese cigarette (6.2±0.2 nmoles of carbonyl/mg BSA) remained unaltered irrespective of whether the charcoal filters were present or replaced by similar length of conventional cellulose acetate filter.
Although charcoal filters are commercially available, those are not effective in reducing the p-BSQ of the smoke. Nevertheless, this invention may be considered a re-evaluation and improvement of the existing state of art. Since activated charcoal not only adsorbs p-BSQ but also some tar and nicotine, the said charcoal filter cigarettes may be categorized as relatively low tar, low nicotine mild cigarettes. Apprehending that there might be some smokers who would not like mild cigarettes with low nicotine delivery, the tobacco of some of the said charcoal filter cigarettes will be fortified with nicotine to produce regular cigarettes with comparable nicotine content without any increase in the p-BSQ level of the smoke.